Post-fire dynamic bond behavior of concrete and deformed bar: Mesoscale simulation and constitutive modeling

Abstract

The mechanical response of reinforced concrete (RC) under the combined action of fire and strain rate differs from that under static load and room temperature, which in turn affects the performance of bond-slip between the reinforcement and concrete. Therefore, the combined effects of the strain rate and fire on the bond performance of RC specimens were discussed by a 3D mesoscale simulation model. In this simulation model, the non-homogeneity of concrete and the external geometric properties of deformed reinforcement were considered. The validity of a mesoscopic simulation model was verified through the successful reproduction of the experiment. On this basis, reinforced concrete's post-fire dynamic bond performance was analyzed. The difference between dynamic bonding properties during high temperature and after cooling down was analyzed. A prediction model for dynamic bond properties was developed considering temperatures and strain rate. It is found that the mesoscale simulation model can demonstrate the process of cracking and the mechanism of failure for the interface bond. The ultimate slip is positively correlated with the temperature or strain rate increased. When the specimen experiences the same temperature, the bond strength increases with the increase of strain rate. However, the bond strength is weakened by high temperatures at a given strain rate. The bonding performance at high temperatures of the specimens is significantly worse than that after cooling conditions from the target temperature. Finally, the formula proposed can effectively predict the post-fire dynamic bonding properties of RC specimen.